1. Field of the Invention
The present invention relates to a piezoelectric transducer. Specifically, the present invention relates to a piezoelectric transducer utilizing piezoelectric elements, such as employed for an automotive control system. More specifically, the present invention relates to a piezoelectric transducer utilizing piezoelectric elements adapted for an automotive combustion sensor.
2. Disclosure of the Prior Art
Japanese Utility Model First Publication No. 53-147666 discloses a common piezoelectric transducer. The transducer comprises two cylindrically formed piezoelectric elements which are laminated with an electrode plate sandwiched therebetween, of which the shape is similar to the piezoelectric elements, an inner support means installed substantially around the inner circumference of the device and an outer support means installed substantially around the outer circumference thereof. Both support means are formed of hard resin or metal. The inner support means has a flange portion adhered to the inner surface of an upper press means.
On the other hand, the outer support means has a flange portion adhered to the inner surface of a lower press means, the upper and lower press means being arranged to oppose each other. Both support means are installed to provide a transformation mode for the laminated piezoelectric elements. Electric power is obtained by a shearing stress, which is applied to the piezoelectric elements when they are subjected to outer pressure in direction perpendicular to the laminated surfaces. As mechanical strength is raised by this support structure, electric power is produced even under relatively high pressure.
However, in this structure, the inner and outer flange portions are installed a little offset from the inner and the outer support means. Therefore, stress concentration frequently occurs where the flanges are not adhered to the elements. At this point, the piezoelectric transducer can not constantly provide electric power and, therefore, reliability of the transducer is relatively low.